scholarly journals Review and numerical investigation of the mean flow features of a round turbulent jet in counterflow

2020 ◽  
Vol 32 (4) ◽  
pp. 045102 ◽  
Author(s):  
Marc Rovira ◽  
Klas Engvall ◽  
Christophe Duwig
Keyword(s):  
Numerical Investigation ◽  
Turbulent Jet ◽  
Mean Flow ◽  
Flow Features ◽  
The Mean

Experimental Investigation of a Turbulent Jet Produced by an Oscillating Surface Actuator

1994 ◽  
Vol 47 (6S) ◽  
pp. S127-S131 ◽  
Author(s):  
R. D. James ◽  
J. W. Jacobs ◽  
A. Glezer
Keyword(s):  
Small Time ◽  
Turbulent Jet ◽  
Linear Functions ◽  
Periodic Excitation ◽  
Mean Flow ◽  
Piezoceramic Actuator ◽  
Mass Injection ◽  
The Mean ◽  
Time Periodic ◽  
Turbulent Water

A round turbulent water jet produced normal to, and at the center of a resonantly driven piezoceramic actuator is investigated experimentally. The flow is produced without mass injection and is comprised entirely of radially entrained fluid. The jet is created by the formation and disappearance of cavitation bubbles during each oscillation cycle near the actuator surface. It appears that this process produces a series of vortex puffs from radially entrained fluid which coalesce to form the jet. Although the jet results from strong time periodic excitation, its time averaged behavior in the far field is similar to that of a classical turbulent round jet in that the increase its width and decrease in the inverse of its centerline velocity are both linear functions of the distance from the actuator. The time periodic features of the jet are observed throughout the flow field and are superimposed on the mean flow. The transient characteristics of the jet have also been investigated and indicate that it can be manipulated on relatively small time scales suggesting that it may be utilized for control of wall bounded shear flows.

Experimental Study of Flow Inside a Centrifugal Fan Using Magnetic Resonance Velocimetry

2019 ◽  
Author(s):  
Davis W. Hoffman ◽  
Laura Villafañe ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Centrifugal Fan ◽  
Mean Flow ◽  
Magnetic Resonance Velocimetry ◽  
Flow Features ◽  
Outlet Flow ◽  
The Mean

Abstract Three-dimensional, three-component time-averaged velocity fields have been measured within a low-speed centrifugal fan with forward curved blades. The model investigated is representative of fans commonly used in automotive HVAC applications. The flow was analyzed at two Reynolds numbers for the same ratio of blade rotational speed to outlet flow velocity. The flow patterns inside the volute were found to have weak sensitivity to Reynolds number. A pair of counter-rotating vortices evolve circumferentially within the volute with positive and negative helicity in the upper and lower regions, respectively. Measurements have been further extended to capture phase-resolved flow features by synchronizing the data acquisition with the blade passing frequency. The mean flow field through each blade passage is presented including the jet-wake structure extending from the blade and the separation zone on the suction side of the blade leading edge.

A vortex-street model of the flow in the similarity region of a two-dimensional free turbulent jet

1982 ◽  
Vol 123 ◽  
pp. 523-535 ◽  
Author(s):  
J. W. Oler ◽  
V. W. Goldschmidt
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Turbulent Jet ◽  
Vortex Street ◽  
Two Dimensional ◽  
Mean Flow ◽  
Mean Velocity ◽  
The Core ◽  
The Mean ◽  
Similarity Relationships

The mean-velocity profiles and entrainment rates in the similarity region of a two-dimensional jet are generated by a simple superposition of Rankine vortices arranged to represent a vortex street. The spacings between the vortex centres, their two-dimensional offsets from the centreline, as well as the core radii and circulation strengths, are all governed by similarity relationships and based upon experimental data.Major details of the mean flow field such as the axial and lateral mean-velocity components and the magnitude of the Reynolds stress are properly determined by the model. The sign of the Reynolds stress is, however, not properly predicted.

scholarly journals INTERACTION OF NON-UNIFORM CURRENTS AND SURFACE HAVES

1984 ◽  
Vol 1 (19) ◽  
pp. 73
Author(s):  
Nabil M. Ismail
Keyword(s):  
Gravity Waves ◽  
Coastal Waters ◽  
Spreading Rate ◽  
Turbulent Jet ◽  
Mean Flow ◽  
Theoretical Predictions ◽  
Current Interaction ◽  
The Mean ◽  
Set Up ◽  
Uniform Currents

Modifications of surface gravity waves and opposing nonuniform currents due to their interaction in coastal waters were experimentally and theoretically investigated. The flow field is modelled as a steady turbulent jet heads directly into the surface waves. Experimental results show that the net waves momentum flux is decreased as waves propagate into the jet which gives rise to mean water set-up towards the jet source. Opposing waves increase the spreading rate of the jet and causes vertical upwelling of the mean flow, near the bottom, towards the free surface. Theoretical predictions of the increase of the jet spreading rate and wave set-up agree with the experimental data. Wave-current interaction modifies significantly waves bottom flow pattern by focusing ambient nearshore waters on the jet outlet.

The Effect of Land Taper Angle on Trailing Edge Slot Film Cooling

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Julia Ling ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Film Cooling ◽  
Concentration Distribution ◽  
Turbine Blades ◽  
Mean Flow ◽  
Trailing Edge ◽  
Taper Angle ◽  
Flow Features ◽  
The Mean ◽  
Slot Film Cooling ◽  
The Impact

Trailing edge slot film cooling is a widely used method of protecting the thin trailing edge of turbine blades from hot gas impingement. The structures that separate the slots, known as “lands,” come in a variety of configurations which can be broadly classified as either “tapered” or “straight.” This paper examines the effect of the land taper angle on the mixing of the coolant flow with the main flow by comparing three configurations: a case with straight lands, a previously reported case with slightly tapered lands, and a case with strongly tapered lands. In each case, the slot width and the land width at the plane of the slot exit are kept constant. For each configuration, the mean volumetric coolant concentration distribution and three-component velocity field were measured using magnetic resonance imaging (MRI) techniques. It is shown that the land taper angle has a strong effect on the mean flow features and coolant surface effectiveness. Furthermore, the impact of the lands configuration on the flow field and concentration distribution is seen not just in the cutback region, but also in the wake of the blade.

Turbulent Shear Flow Over Surface Mounted Obstacles

1990 ◽  
Vol 112 (4) ◽  
pp. 376-385 ◽  
Author(s):  
W. H. Schofield ◽  
E. Logan
Keyword(s):  
Shear Flow ◽  
Shear Layers ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Mean Flow ◽  
Wide Range ◽  
Flow Features ◽  
Model Geometry ◽  
The Mean ◽  
High Reynolds

The mean flow field surrounding obstacles attached to a wall under a turbulent boundary layer is analyzed. The analysis concentrates on how major features of the flow are influenced by model geometry and the incident shear flow. Experimental data are analyzed in terms of nondimensionalized variables chosen on the basis that their effect on major flow features can be simply appreciated. The data are restricted to high Reynolds number shear layers thicker than the attached obstacle. The work shows that data from a wide range of flows can be collapsed if appropriate nondimensional scales are used.

Experimental Study of Flow Inside a Centrifugal Fan Using Magnetic Resonance Velocimetry

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Davis W. Hoffman ◽  
Laura Villafañe ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Centrifugal Fan ◽  
Mean Flow ◽  
Magnetic Resonance Velocimetry ◽  
Flow Features ◽  
Outlet Flow ◽  
The Mean

Abstract Three-dimensional (3D), three-component time-averaged velocity fields have been measured within a low-speed centrifugal fan with forward curved (FC) blades. The model investigated is representative of fans commonly used in automotive applications. The flow was analyzed at two Reynolds numbers for the same ratio of blade rotational speed to outlet flow velocity. The flow patterns inside the volute were found to have weak sensitivity to Reynolds number. A pair of counter-rotating vortices evolves circumferentially within the volute with positive and negative helicity in the upper and lower regions, respectively. Measurements have been further extended to capture phase-resolved flow features by synchronizing the data acquisition with the blade passing frequency. The mean flow field through each blade passage is presented including the jet-wake structure extending from the blade and the separation zone on the suction side of the blade leading edge.

scholarly journals Effect of background turbulence on an axisymmetric turbulent jet

2013 ◽  
Vol 736 ◽  
pp. 250-286 ◽  
Author(s):  
B. Khorsandi ◽  
S. Gaskin ◽  
L. Mydlarski
Keyword(s):  
Mass Flow Rate ◽  
Flow Rate ◽  
Reynolds Numbers ◽  
Turbulent Jet ◽  
Mean Square ◽  
Mean Flow ◽  
Velocity Measurements ◽  
Background Turbulence ◽  
The Mean ◽  
Different Levels

AbstractThe effect of different levels of background turbulence on the dynamics and mixing of an axisymmetric turbulent jet at different Reynolds numbers has been investigated. Approximately homogeneous and isotropic background turbulence was generated by a random jet array and had a negligible mean flow (${\langle {U}_{\alpha } \rangle }/ {u}_{\alpha \mathit{rms}} \ll 1$). Velocity measurements of a jet issuing into two different levels of background turbulence were conducted for three different jet Reynolds numbers. The results showed that the mean axial velocities decay faster with increasing level of background turbulence (compared with a jet in quiescent surroundings), while the mean radial velocities increase, especially close to the edges of the jet. Furthermore, the axial root-mean-square velocities of the jet increased in the presence of background turbulence, as did the jet’s width. However, the mass flow rate of the jet decreased, from which it can be inferred that the entrainment into the jet is reduced in a turbulent background. The effect of background turbulence on the entrainment mechanisms is discussed.

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